This invention relates to masks which are employed in vapor deposition processes to form desired patterns of deposited materials, and it relates particularly to masks which are designed to form patterns containing very closely spaced parts, such as the sets of parallel conductors that are deposited upon glass plates in gas panel display devices, for example.
Masks of the kind just described must be thin enough to produce high-resolution patterns; yet they also must maintain accurate positioning of parts which have little or no inherent rigidity, such as the very narrow strips separating the closely spaced slots through which gas panel conductors are to be deposited. To hold such parts in place, the mask may be provided with reinforcing ribs that extend across the closely spaced openings and are integral with or joined to the intervening parts which narrowly separate these openings. However, the provision of such ribs is likely to introduce a problem which could be described as "shadowing" or the "stencil effect". At each point where a reinforcing rib extends across a relatively narrow opening in the mask, the rib will tend to obstruct the deposition of vaporized coating material through that opening. In commonly used line-of-sight deposition processes such as electron beam deposition, the presence of such an obstruction across a narrow opening will cause a void or thin spot to appear in the deposited pattern, thereby complicating the task of fabricating an acceptable pattern.